A Novel Contrast Medium Targeting Of Carbonic Anhydrase Ⅸ(CAⅨ-Mn) On Magnetic Resonance Imaging Of Esophageal Squamous Cell Carcinoma Xenograft In A Nude Mice Model:an Experimental Study

Objective:To detect the difference of carbonic anhydraseⅨ(CAⅨ)between in cancer tissues and adjacent tissues of patients with esophageal squamous cell carcinoma(ESCC)by using real-time quantitative polymerase chain reaction(QPCR)technology.,And to explore the targeting of a novel contrast medium targeting of carbonic anhydraseⅨ(CAⅨ-Mn)in the imaging of ESCC xenograft in nude mice.Methods:·The cancer tissues and adjacent tissues of 3 patients with ESCC were collected,and the mRNA content of CAⅨ in each tissue was detected by qPCR technology.·The relaxivity of CAⅨ-Mn was measured on 0.4T magnetic resonance scanner at 32℃ by preparing gradient concentrations of contrast agent which were calibrated with inductively coupled plasma mass spectrometer(ICP-MS).·The cytotoxicity of the new CAⅨ-Mn contrast agent on RAW246.7 cell line was tested by cell counting kit-8(CCK-8)method·The Eca-109 ESCC cell line was incubated and injected at the logarithmic growth phase into the ventral subcutaneously of the left hind limb of 12 nude mice.The tumor model mice were reared under SPF condition(20～26℃,40%～70%humidity)until the tumor grows to a diameter of about 5-10 mm.The experimental group(n=6)was scanned with CAⅨ-Mn(dose:100μmol/kg)for enhanced T1 weighted imaging(T1WI)at 3.0 T MR scanner,and the control group(n=6)scanned with Gadopentate Meglumine with same dose.The signal intensity was measured before and after contrast agent injection at different time points(2,4,6,8,10,30,40,50 and 60min).The corresponding Contrast-to-Noise Ratio(CNR)values at each time point were calculated.The paired t test was used to analyze the difference in signal between the two contrast agents;the independent sample t test was used to analyze the difference in tumor CNR between the two contrast agents at each time point.Results:The expression of CAIX in ESCC tissue was significantly higher than that in adjacent tissue(p<0.05).The longitudinal relaxivity(r1)of CAⅨ-Mn is 6.750 mM-1s-1(32℃,0.5 T).Cytotoxicity assays showed a cell survival rate of 79.4%for 48h at a contrast agent concentration of 0.1 mmol/L.Magnetic resonance imaging of experimental group(CAⅨ-Mn):The SI of the tumor gradually increased and reached the highest point at 30 minutes;The CNR value was 26.923±8.568;Control group(gadopentetate dimeglumine):the SI of tumor gradually increased and reached the highest point at 4 minutes;The CNR value was 16.997±9.161.The CNR values of the experimental group were higher than control group at 10,30,40,50 and 60 minutes after injection of contrast agents and the difference was statistically significant(P<0.05).Conclusion:1)The mRNA expression of CAⅨ in ESCC tissue was significantly higher than that in adjacent tissue.2)The CAⅨ-Mn had high longitudinal relaxation efficiency,low cytotoxicity,and good biocompatibility.3)T1WI of carcinoma xenograft in nude mice shows that CAⅨ-Mn can produce higher CNR value compared with gadopentetate dimeglumine at 10-60min,which proved that CAⅨ-Mn had a certain targeting property and specificity for targeting to carbonic anhydrase Ⅸ.